I really like the smaller cordless impacts, when I bought the 1/2" Makita it was a choice between the made in Japan uber powerful 9lb tool or the small 1/2" 5lb tool (inc 5A battery), it is the same size as the 1/4 and 3/8", very light and powerful enough. I went with the small one and don't regret it.
For the big stuff I have powerful air guns up to 1" drive, the 1/2" has more power, weighs 4lb less and 2" smaller than the big cordless.
The problem with big guns cordless or air is using them under the hood, its almost impossible with today's cramped engine bays, the small gun gets in so many places the big one wont go, basically relegating them to under the car work.
For body panels, interior bolts, hinges and so on the small one really shines, no air hose getting dragged into the interior to get seat belt and seat bolts. Other tools are mains electric like angle grinders, big drills and sheet metal shears.
One type of tool is not better than another for all jobs, they all have their place in the box.